Will these impacted teeth respond?

Published: December 2015

Bulletin #50 December 2015

Will these impacted teeth respond to
extrusive mechanics?

It is probably true to say that,
when an experienced orthodontist looks at the teeth of a child with a
malocclusion, for the most part he/she more or less immediately forms a mental
and tentative treatment plan that will bring the teeth into alignment and into
occlusion. The orthodontist is rarely concerned with the possibility that the
teeth may not respond to orthodontic forces. The reason for this is that, if
the teeth have erupted autonomously into the oral environment, it may be safely
assumed that they have a normal attachment to the supporting tissues and
therefore can be successfully moved using suitable orthodontic appliances.

In a
malocclusion that features an impacted tooth, many of us will study the
2-dimensional view of the ectopic tooth, assess how the tooth may be brought
into place in the arch and may even set about arranging for the surgeon to
expose it before any other form of treatment is initiated. Unless spontaneous
eruption of the tooth is expected, this line of action ignores the possibility
that the tooth will not respond to traction forces and the fact that there is
the need for a solid anchorage base from which to apply these forces.1

The first and most important
prerequisite that needs to be addressed in these cases is to find the reason
that the tooth has failed to erupt. This is not a theoretical or academic
question. Accurate diagnosis of the cause is usually the key to deciding if the
tooth can be moved and, from there, to success in its treatment.

The most common reason is an
obstruction that lies directly in the path of the tooth’s progress – a
condition which may be termed mechanical failure of eruption (MFE). Often, an
adjacent tooth is to blame, which may take the form of non-resorption or
eccentric partial resorption of a deciduous predecessor, or an overall
condition of crowding or a supernumerary tooth. It is something of a relief to
know when this is the etiology, since its elimination in general provides a
good prognosis for potential resolution of the impaction. On the other hand, if
the diagnosis is primary failure of eruption (PFE), then there is no chance of
the tooth ever erupting or being mechanically erupted, whether or not there is
space.

There are also occasional instances
where the diagnosis is not possible to determine, for lack of any of the
clinical and radiographic signs that one can usually expect to find.This month’s bulletin is devoted to the
description of such a case, with non-eruption of the teeth in the mandibular
right premolar/molar area, whose etiology and diagnosis were unknown.

In the absence of a diagnosis, the sole
approach available to the orthodontist is to treat the case empirically. Essentially,
this means applying a force and attempting to move each tooth individually. Why
individually, you ask? If one of the teeth refuses to respond, it will prevent
the others from moving if they are in any way linked together. It should be
remembered that the unwanted side effect of using a continuous archwire to
erupt a single resistant impacted tooth, will be to intrude the adjacent teeth.
In these circumstances, we cannot offer the patient an assessment of the
chances of success until we have completed several months of treatment to align
and level, to open space, to insert a full thickness base arch wire and begin
applying traction to the tooth. Only after the extrusive force has been active
for several weeks or months will we learn whether the tooth shows signs of
movement or not …… and the outcome may be total disappointment, particularly if
there was little or no real malocclusion to treat, aside from the impacted
tooth.

Case report

Fig. 1a, b. The initial condition in August 2008 at age
13 years shows the largely edentulous mandibular right side. Cusp tips of #43
and #47 are barely discernible.

Fig. 1c. The panoramic view taken in July 2005. Note the
presence of bone covering the lower molars and premolars. The mandibular right
first permanent molar has strongly distally-curved roots, with the apices close
to the lower border of the mandible.

The patient was a 13 year old male
who was referred to me by an orthodontist in his small home town in the south
of Israel.At the first examination
(Fig. 1a, b), his father pointed out that the two deciduous molars of the
maxillary left and the two deciduous molars of the mandibular right quadrants had
been extracted several years earlier, at age 5 years, due to caries. As the
result, the maxillary first permanent molar had drifted mesially. However, in
the mandibular right quadrant, no premolar nor permanent molar teeth had
erupted in the eight years since the extractions were done. Only the two buccal
cusps of the second

mandibular permanent molar were partially visible on that
side. In contrast, all the permanent teeth on the left side in the mandible,
from canine to second molar, were erupted. Furthermore, all the unopposed teeth
of the affected right side of the maxillary dental arch had markedly
over-erupted, with the first maxillary permanent molar in occlusal contact with
the mucosa of the opposite jaw. This resulted in a distinct cant in the
occlusal plane in which the right side was approximately 7-8mms lower than the
left.

A panoramic radiograph was
commissioned at that time, from which it was noted that all the permanent teeth
in both jaws, were seen to be developing, including third molars. It is pertinent
to point out that the film was executed with conventional screen film
radiography, in 2008. As the result, there was only a single printed original
film and this was lost in the patient’s several round trips between
orthodontist and oral surgeon. This was an unfortunately relatively common
occurrence when a patient was treated by different specialists, until digitally
imaged panoramic films permitted computerized and internet duplication to
provide copies for all concerned. For this reason, that critically important
film is presently missing from this account of the case, although it was
available at the time!

However, an earlier film was
available, taken by another practitioner at age 10 years, elsewhere. This can
be seen in Fig. 1c. Studying the relative development of the roots of the
erupted and unerupted permanent teeth, the overall dental age of the patient
was clearly younger than his years and estimated to be 8.5 years. The maxillary
incisor root apices were still open and the premolar and second permanent
molars roots were less than one third developed. The canine and premolars of the lower right
side were covered by alveolar bone. Extrapolating the expected root growth from
this 10 year old depiction to the 13 year old boy seen at the first
examination, would lead us to expect eruption of these teeth, given that they
would have ½ to ¾ of their expected final root length.

N.B. For
an explanation of how to assess dental age, please refer to Chapter 1 of my text
“Orthodontic Treatment of Impacted Teeth” as advertised on the right hand
column of this page.

The unerupted mandibular right
first molar roots were turned distally to an exaggerated degree, with the
apices in close proximity to the mandibular lower border. Its crown was covered
with a fairly thick layer of bone.

This film and the intra-oral
photographs confirmed the non-eruption of the first permanent molar, but the
crucial question is: why should this be? That very early extraction of the
deciduous molars had resulted in delayed eruption of the premolars is easily
understood and accepted. However, a first permanent molar has no deciduous
predecessor and it seems most unlikely that trauma could have played a part in
its impaction, given its very posterior location in the mouth and no supporting
history. Why, too, did the roots develop with this strong distal curvature and,
more importantly, why were the root apices located in close proximity to the
lower border of the mandible?

These are features that are usually associated
with pathologic processes which prevent the vertical development and eruption
of the tooth while perhaps permitting adjacent area growth, such as ankylosis
or invasive cervical root resorption, or perhaps primary failure of eruption
which also influences adjacent and more distal areas.

Dr. Sylvia Frazier-Bowers, Associate Professor in
Orthodontics at the University of North Carolina, Chapel Hill has
pointed out in recent personal correspondence that“
…….. an evidence-based approach to evaluate eruption disorders 2 is
available, by applying a straightforward rubric to determine if PFE can be
ruled out.While an analysis of the
PTH1R gene is not 100% diagnostic, due to a likely heterogeneity of PFE, it is
still a good first step to take if available.However, there are some cases that can be ruled out due to pathology
and/or a mechanical failure of eruption (MFE).Based on the diagnostic rubric described recently, 2 the
first feature that should be addressed is whether the bony pathway is
completely cleared.If it is not
completely cleared then it is not PFE. In these cases exposure of the tooth and
orthodontic traction should result in successful tooth movement”.As can be seen (Fig. 1c) the bony pathway in
the present case was not clear at the outset.

The presence of these factors,
recognized at the outset, should serve to make the cautious and prudent
orthodontist wary of offering more than a very guarded prognosis for the
chances of successfully raising this tooth. On the other hand, the maxillary
posterior teeth had all over-erupted to a marked degree and were contacting the
mucosa covering the mandibular teeth, rendering rehabilitation of the entire
right side and the establishment of a functional working unit, highly
problematic.

It was clear that, with successful
treatment, the patient had very much to gain and very little to lose in the
event of failure.There was no way to
use conventional orthodontics to establish dental anchorage from the already
over-erupted maxillary teeth , which meant that skeletal anchorage remained the
only option both for raising the mandibular teeth and for intruding the
maxillary teeth.

3.Apply extrusive force to
the mandibular premolars and first molar using vertical (up-and-down) elastics
from the bonded attachment hooks to the zygomatic plate TAD and placed by the patient

4.Apply intrusive force to
the maxillary molars and premolars using elastic chains from the brackets of the maxillary teeth/archwire to the TAD

5.Following the hoped-for
eruption, a full lower fixed appliance to level and align mandibular teeth.

The maxillary fixed appliance was
placed in October 2008. The surgical episode was successfully performed by
Prof. Nardy Caspi, in all its parts (Fig. 2), at the beginning of December 2008
and under general anesthesia.

Fig. 2a. December 2008. A broad occluso-buccal flap was
reflected to immediately reveal the canine, first premolar and second molar.

Fig. 2b. The second premolar and first molar were exposed
following removal of their bony cover.

Fig. 2d. The flap was re-sutured back to its former
place, with only the two twisted ligatures visible. These were shortened and
fashioned into two traction hooks. Note the open exposure of the canine, first
premolar and second molar.

The canine, first premolar and second molar were
merely exposed in an open surgical procedure (Fig. 2a), while attachments were
placed on the deeper second premolar and first molar (Fig. 2b-d).

Fig. 3. The zygomatic plate screwed into place on the
inferior aspect of the zygomatic process of the maxilla.

Fig. 4. Elastic traction is applied direct from the
traction hooks to the zygomatic plate.

The zygomatic
plate was screwed into place at the same surgical session (Fig. 3). Vertical
elastic traction individually to these teeth was initiated I week later and
placed by the patient (Fig. 4). At this time, the maxillary dentition was well
aligned and leveled and a heavy 0.020” round archwire was in place. At each
visit in the maxilla, an elastic chain was placed either direct on the molar
tube and premolar brackets or on the archwire itself and intrusive force
applied by stretching it to the TAD.

Fig. 5a. January 2011. Intra-oral views to show the final
alignment, with corrective leveling of the occlusal plane.

The impacted teeth responded very
favorably to the extrusive traction and, by late September 2009, they were
sufficiently erupted for a full multibracketed orthodontic appliance to be
placed and the remainder of the, then, routine orthodontic treatment was
undertaken and completed in January 2011, when the appliances were removed (Fig
5). Removable retainers were placed at
the end of treatment, with instructions that they be worn at night – advice
that was totally ignored by the patient!

During the treatment and following
a traumatic incident to the patient’s maxillary anterior teeth, a root canal
treatment became necessary and the tooth subsequently acquired a blue-grey hue.

Fig. 6. Panoramic of the dentition in July 2015, 4.6 years post-treatment.

The patient was seen again only in
May 2013, when a minor degree of incisor crowding relapse was noted, for which
the patient refused treatment. In July 2015 , he was seen by the original oral
surgeon (Prof. Nardy Caspi) who extracted his wisdom teeth (Fig. 6).

Acknowledgement

I am grateful to Dr. Sylvia Frazier-Bowers for her scholarly input for this bulletin.